1. Field
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, to a light emitting diode and a method of fabricating the same.
2. Discussion of the Background
A light emitting diode (LED) is a semiconductor device that emits light, and has characteristics of eco-friendliness, low voltage, long lifespan and low costs. Conventionally, LEDs were frequently applied to a lamp for a display, or a display of simple information such as numbers. However, with the development of industrial technologies, particularly information display and semiconductor technologies, the LEDs have recently used in various fields such as display, vehicle headlamp and projector fields.
Particularly, a gallium nitride (GaN)-based compound semiconductor is used for a visible or ultraviolet light emitting device, a high-power electronic device, or the like. A GaN-based compound semiconductor layer is generally grown on a substrate by using a growth method such as molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HYPE).
The GaN-based compound semiconductor layer is generally grown on a heterogeneous substrate such as a sapphire substrate. Particularly, the GaN-based compound semiconductor layer is grown on a sapphire substrate having c-plane as a growth surface. The nitride semiconductor layer and the heterogeneous substrate have different lattice constants and different thermal expansion coefficients. Therefore, when the nitride semiconductor layer is grown on the heterogeneous substrate, many crystal defects occur in the nitride semiconductor layer.
These crystal defects cause deterioration of the characteristics of an electronic device or light emitting device including the nitride semiconductor layer, e.g., light emitting efficiency of the light emitting device.
Moreover, a GaN-based compound semiconductor layer grown in the c-axis direction has a polarity caused by spontaneous polarization and piezoelectric polarization. Therefore, the recombination rate of electrons and holes is lowered, and there is a limitation in improving the light emitting efficiency.
Meanwhile, another GaN-based compound semiconductor layer grown on a-plane or m-plane is non-polar, so that the spontaneous polarization or piezoelectric polarization does not occur in the GaN-based compound semiconductor layer. However, the growth of the GaN-based compound semiconductor layer on a-plane or m-plane has many problems to be solved, and therefore, has not been widely applied yet.
Meanwhile, semiconductor devices including LEDs are fabricated using various semiconductor device fabricating apparatuses, e.g., an inductively coupled plasma (ICP) apparatus, a plasma enhanced chemical vapor deposition (PECVD) apparatus, an electron-beam (E-beam) apparatus, a photolithography apparatus, and the like.
When the semiconductor devices are fabricated, a cassette in which a plurality of substrates are stacked in layers is used for the purpose of convenience in transferring and keeping the substrates.
However, in order to massively produce semiconductor devices, particularly LEDs, there have been many cases where a process is performed by loading a plurality of substrates into a semiconductor device fabricating apparatus. In this case, the semiconductor substrates stacked in layers are extracted one by one from a cassette and then loaded into the semiconductor device fabricating apparatus.
Accordingly, since the individual substrates are loaded one by one into the semiconductor device fabricating apparatus, there is a problem in that much loading time is required.